apache-comnons系列之commons-pool2.4 学习笔记

概述

• 参考
  
  • http://www.jianshu.com/p/b0189e01de35
  • https://my.oschina.net/xinxingegeya/blog/391560
  • https://segmentfault.com/a/1190000003920723
  • https://www.idaima.com/article/1975
• ObjectPool—-A pooling simple interface.
  
  • GenericObjectPool
    
    • A configurable {@link ObjectPool} implementation.
  • GenericObjectPoolConfig
    
    • A simple “struct” encapsulating the configuration for a {@link GenericObjectPool}.
• KeyedObjectPool—-A “keyed” pooling interface.
  
  • GenericKeyedObjectPool
    
    • A configurable KeyedObjectPool implementation.
  • GenericKeyedObjectPoolConfig
    
    • A simple “struct” encapsulating the configuration for a {@link GenericKeyedObjectPool}.
• BaseGenericObjectPool
  
  • Base class that provides common functionality for {@link GenericObjectPool} and {@link GenericKeyedObjectPool}. The primary reason this class exists is reduce code duplication between the two pool implementations.
• BaseObjectPoolConfig
  
  • Provides the implementation for the common attributes shared by the sub-classes. New instances of this class will be created using the defaults defined by the public constants.
• GenericObjectPoolMXBean
  
  • Defines the methods that will be made available via JMX.
• PooledObjectFactory
  
  • An interface defining life-cycle methods for instances to be served by an {@link ObjectPool}.
    
    • BasePooledObjectFactory
  • A base implementation of PoolableObjectFactory.
• PooledObject
  
  • Defines the wrapper that is used to track the additional information, such as state, for the pooled objects. Implementations of this class are required to be thread-safe.
    
    • DefaultPooledObject
  • This wrapper is used to track the additional information, such as state, for the pooled objects.
• PooledObjectState
  
  • Provides the possible states that a {@link PooledObject} may be in.
    
    • IDLE/ALLOCATED/EVICTION/ABANDONED/RETURNING
• PoolUtils
  
  • This class consists exclusively of static methods that operate on or return ObjectPool or KeyedObjectPool related interfaces.

测试

• org.apache.commons.pool2.impl.TestDefaultPooledObject
  
  • allocate
    
    • Allocates the object.
    • synchronized/state = PooledObjectState.ALLOCATED;/lastBorrowTime/lastUseTime/borrowedCount
  • deallocate
    
    • Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE} if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}.
    • synchronized/state = PooledObjectState.IDLE;/lastReturnTime
• org.apache.commons.pool2.TestBasePoolableObjectFactory
  
  • All operations defined here are essentially no-op’s.
  • abstract T create()
  • abstract wrap(T obj);
• org.apache.commons.pool2.impl.TestGenericObjectPool
  
  • allObjects
  • idleObjects
  • ONAME_BASE
  • abandonedConfig
  • borrowObject
    
    • quivalent to {@link #borrowObject(long) borrowObject}({@link #getMaxWaitMillis()}).
    • idleObjects
    • idleObjects.pollFirst();
    • create
  • returnObject
    
    • If {@link #getMaxIdle() maxIdle} is set to a positive value and the number of idle instances has reached this value, the returning instance is destroyed.
    • factory.validateObject(p)
    • factory.passivateObject(p);
    • idleObjects.addFirst(p);
    • updateStatsReturn(activeTime);
  • create
    
    • Attempts to create a new wrapped pooled object.
    • p = factory.makeObject();
    • createdCount.incrementAndGet();
    • allObjects.put(new IdentityWrapper(p.getObject()), p);
  • destroy
    
    • Destroys a wrapped pooled object.
    • toDestory.invalidate();
    • idleObjects.remove(toDestory);/
    • allObjects.remove(new IdentityWrapper(toDestory.getObject()));
    • factory.destroyObject(toDestory);
  • invalidateObject
    
    • Activation of this method decrements the active count and attempts to destroy the instance.
  • clear
    
    • Clears any objects sitting idle in the pool by removing them from the idle instance pool and then invoking the configured {@link PooledObjectFactory#destroyObject(PooledObject)} method on each idle instance.
    • idleObjects.poll();
    • destroy(p);
• org.apache.commons.pool2.impl.TestGenericKeyedObjectPool
  
  • keypool类似于pool,不同之处在于对同一key的操作委托给了ObjectDeque
  • 同时多了key的添加与已移除
  • poolMap
  • poolKeyList
  • keyLock
  • ONAME_BASE
  • ObjectDeque
    
    • Maintains information on the per key queue for a given key.
    • idleObjects
    • allObjects
    • createCount
  • borrowObject
    
    • register(key);
    • p = objectDeque.getIdleObjects().pollFirst();
    • p = create(key);
    • deregister(key);
  • register
    
    • Register the use of a key by an object.
    • register() and deregister() must always be used as a pair.
    • poolMap.get(k);
    • objectDeque.getNumInterested().incrementAndGet();
  • deregister
    
    • De-register the use of a key by an object.
    • register() and deregister() must always be used as a pair.
    • poolMap.get(k);
    • objectDeque.getNumInterested().decrementAndGet();
  • create
    
    • Create a new pooled object.
    • objectDeque = poolMap.get(key);
    • p = factory.makeObject(key);
    • objectDeque.getAllObjects().put(new IdentityWrapper(p.getObject()), p);
  • TestPoolUtils
  • checkMinIdle
    
    • Periodically check the idle object count for the key in the keyedPool. At most one idle object will be added per period. If there is an exception
    • when calling {@link KeyedObjectPool#addObject(Object)} then no more checks for that key will be performed.